Luciferase is a luminescence enzyme which catalyzes oxidation of luciferin, thus allowing it to emit a light. Luciferase derived from fireflies, such as GENJI firefly, HEIKE firefly, American firefly, etc., requires ATP, etc., for the luminescence of luciferin, and owing to this property, luciferase is used for the quantitative determination of a trace amount of the above-mentioned ATP, etc.
However, since luciferase is generally unstable to heat, this enzyme has the defect of being liable to be inactivated in storage as a reagent. As a means of avoiding this disadvantage, the addition of a salt, etc., makes it possible to store luciferase stable to some extent. In this case, however, the presence of the salt sometimes leads to another disadvantage, i.e. hindrance of luciferase reaction.